Homologation of Isocyanates with Lithium Carbenoids: A Straightforward Access to α-Halomethyl- and α,α-Dihalomethylamides
Vittorio Pace*, Laura Castoldi, Ashenafi Damtew Mamuye, Wolfgang Holzer
*Department of Pharmaceutical Chemistry - Division of Drug Synthesis, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria, Email: vittorio.paceunivie.ac.at
V. Pace, L. Castoldi, A. D. Mamuye, W. Holzer, Synthesis, 2014, 46, 2897-2909.
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Treatment of widely available isocyanates with monohalolithium and dihalolithium carbenoids provides α-halo- and α,α-dihaloacetamide derivatives. While monohalolithium carbenoids can be prepared by a smooth lithium-halogen exchange, the preparation of the corresponding dihalo compounds proved to be highly dependent on the base used to realize the deprotonation, with lithium 2,2,6,6-tetramethylpiperidine emerging as optimal.
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